PHENOTYPE METASTABILITY IN BACTERIA

This review analyzes data available in the literature and the author's own data on the phenotypic variability of bacteria that occurs within the framework of a genotype unchanging in terms of the genetic inform ation stored. This variability is a form of bacterial adaptation to an unstable environment and results from a specific form of natural sele ction. This phenomenon arose evolutionarily not as a mechanism to prov ide genetic diversity for the divergence process but as a mechanism of species stabilization; therefore, it was termed phenotype metastabili ty. It includes, as specific variants, processes known as phase and an tigenic variations, R-S-M dissociation, phenotype conversion, etc. The mechanisms of phenotype metastability are extremely diverse. They inc lude alternative expression (of the switch on-switch off type) of indi vidual genes or small groups of genes; variation in the composition of synthesized proteins controlled at the level of transcription; expres sion of complex phenotypes adapted to different environmental conditio ns that involves phage transposition, reading-frame-shift mutations, e tc. The phenomenon of phenotype metastability is widespread among bact eria.